On top of everything, it is OPEN SOURCE, so if you have an idea for a feature, feel free to submit pull request.
I recommend that you uncheck everything under Notifications in Pebble app, so you won't get conflicts. If you don't use PebbleDialer, you can keep "Incoming Calls" checked, of course.
If you don't use features listed above, feel free to disable those permissions with any permission-disabling app. If you are still paranoid, you can check source code and build it yourself.
After you enable notification service and install watchapp, you will get all notifications by default. You can filter by app or by keyword/regex in phone app.
When you receive notification, you will get interface very similar to Pebble's native one. Controls are also slightly altered:
UP = Scroll up
Double press UP = Previous notification (moves to left)
SELECT = Dismiss notification (just removes notification if dismissing is not available)
DOWN = Scroll down
Double press DOWN = Next notification (moves to right)
BACK = Exit notification window (if you do that accidentally, just re-open app and see notifications from history).
Pebble is a not really good at displaying international characters. That is why Notification Center allows you to replace specific characters with normal ones to basically translate messages from international to regular characters.
To enable this feature, you have to enter all replacement pairs into Notification Center. You can do this from app itself, but it can become tedious if there are many characters. Other way of doing it is creating dictionary on PC and transferring it to the phone or even using pre-made dictionary.
Format is simple txt file and it goes like this: "original > replacement". For example "a > b" would mean every a in every message will be replaced with b. To make files more compatible, it is recommended to use unicode codes on the left side instead of plain text characters.
To import table into NC, place them into NotificationCenter folder on your phone's internal storage and use Import menu option.
(If you made translation table for your language's special characters, feel free to make post about it and I will add it to above table).